1. Field of the Invention
The present invention relates to a method for producing 5′-guanylic acid and a novel microorganism used for this production. 5′-guanylic acid is useful as a seasoning, in medicines and as a raw material thereof.
2. Brief Description of the Related Art
Known methods for industrially producing 5′-guanylic acid, also known as guanosine-5′-monophosphate, or “GMP”, include producing guanosine by fermentation and then subjecting it to enzymatic phosphorylation, to obtain 5′-guanylic acid (JP 07-231793, JP 10-201481, WO96/37603, and JP 2001-245676).
In addition, other methods of producing GMP have been reported, including culturing both a microorganism belonging to the genus Escherichia with increased GMP synthetase activity and a Brevibacterium ammoniagenes which is able to biosynthesize large amounts of adenosine triphosphate (ATP) (hereinafter referred to as the “regeneration of ATP”) in a culture medium containing 5′-xanthylic acid (XMP) and ammonia or glutamine. ATP is generated by glucose metabolism and is necessary for the synthesis of GMP from 5′-xanthylic acid (XMP), and GMP is generated and accumulated in the medium by converting XMP to GMP with high efficiency (Tatsuro Fujio et al., Biosci. Biotech. Biochem., 1997, Vol. 61, No. 5, p. 840-845).
Methods for producing GMP by fermentation have also been suggested. For example, JP 56-12438 discloses a method for producing GMP wherein a mutant strain of the genus Bacillus having adenine auxotrophy and resistance to decoyinine or methionine sulfoxide is cultured, followed by collecting the GMP that is generated from the medium. Also, JP 2002-355087 discloses a method for producing GMP characterized by culturing a strain of bacteria belonging to the genus Escherichia which is able to produce inosinic acid (inosine 5′-monophosphate, hereinafter referred to as “IMP”), wherein two types of 5′-nucleotidase genes are deleted and the IMP dehydrogenase and GMP synthetase genes are amplified, and collecting the GMP that is generated from the medium. Yet, in general, direct fermentation of GMP does not provide a sufficient yield and is not necessarily practical compared with the above-described enzymatic method.
Thus far, production of GMP from IMP as a raw material by using bacteria belonging to the genus Escherichia with enhanced activities of IMP dehydrogenase and GMP synthetase has not been previously reported.